The purpose of this story is twofold. First, the KTM 300 is the second-biggest seller in KTM’s lineup, and we love this motorcycle. Second, two-stroke exhaust pipes are a consumable item. They will get smashed and need replacing. It’s also good to know that the stock KTM chamber makes truly broad and very balanced power. It really has no weaknesses, other than that it’s a very lightweight unit and, like all two-stroke chambers, can get tweaked easily in a crash or brush with a boulder. We learned that each of the aftermarket exhaust systems modifies the powerband and, depending on what you’re looking for, can really help or hinder the performance. We evaluated each of them using the stock KTM muffler, just to keep everything apples to apples. After the expansion chamber test, we evaluated several mufflers too.
When the time comes to replace that smashed pipe, FMF’s most popular exhaust pipe is the Fatty. It is constructed from carbon steel with a nickel-plated finish to provide increased durability. The pipe is built using their Truffle stamping process to ensure a proper fit. All of the mounting brackets were dead-on (meaning it went on easily), and FMF provides a set of new O-rings with the pipe.
If you like the way your OEM exhaust performs, then you’ll like the Fatty. It provides a smoother transition from bottom to mid, making the area that most riders use a little friendlier. The top signs off slightly sooner than the stocker, but it’s only apparent when trying to pull a gear too long or on a motor-melting hill-climb. As a do-it-all pipe, the Fatty is our top choice.
The Gnarly was designed to withstand off-road abuse, plain and simple. Its thicker steel shell will take a hit far better than any other two-stroke pipe on the market. The second notable feature of the Gnarly is that FMF moved the power down lower. The initial roll-on is super enhanced, targeting tight and nasty terrain. The Gnarly is constructed from carbon steel that’s been nickel-plated using Tru-Flow stamping. The fit was perfect, and new O-rings are included. The Gnarly is made from very thick steel and is definitely heavier than any other pipe in the test.
With this pipe, the power pulses are completely changed. Cruising along at idle in first or second gear and snapping the throttle open will result in an instant rush of forward momentum. The bottom-to-mid torque increase is dramatic. As expected, the top end signs off pretty early. For brutal technical riding, the Gnarly is our pipe of choice. Surprisingly, this pipe also worked well on motocross tracks with jumps right out of tight turns. It allowed the rider to carry a taller gear through a corner then, with a quick stab at the clutch, launch over jumps. They say that the torque of a four-stroke makes you lazy when riding motos. Putting a Gnarly on your two-stroke can have the same effect.
PRO CIRCUIT PLATINUM 2
Mitch Payton’s Pro Circuit Racing has been around since 1978. In that 36-year time span, the boys at PC have learned a bit about two-stroke exhaust systems. The Platinum 2 pipe is constructed from stamped, 18-gauge carbon steel, which is coated using their Electroless nickel-plating process to increase durability. The pipe has brazed nuts on both of its mounting brackets. This is a nice feature since it means you don’t have to remove the OEM slip nuts from your old exhaust. All of the pipe brackets lined up perfectly, and it’s compatible with the stock muffler.
As with all of the aftermarket exhausts in this test, the Platinum 2 moves the power in the rpm range. There is a little less grunt on the bottom, with a smooth transition to the midrange. Once the motor gets into the midrange, there’s a meaty surge in power that is a precursor of things to come. The top-end performance gains with this exhaust feel huge on the track. In addition to the power gains, there’s more over-rev available, allowing you to pull a gear longer before shifting. This pipe requires the rider to keep the rpm up, as it won’t pull with authority down low. The pipe really rewards the rider who keeps things spinning in the mid-to-upper rpm range. The Platinum 2 is a great choice for fast motos and high-speed off-road.
Scalvini may not be a household name in the U.S., but it’s a major player in the exhaust wars in Europe. The easiest way to describe this pipe is “moto art.” Those of us old enough to have been around during the days of factory two-strokes remember that a hand-welded cone pipe was an object of desire. The big hitters in U.S. exhausts, Donny Emler and Mitch Payton, started their companies by building this style of exhaust pipe. The task of cutting individual strips of metal and hand-rolling and -welding them into an exhaust is extremely labor-intensive and costly. Scalvini is still building their pipes the old-fashioned way. The cost is elevated, but so are the performance gains. The easiest way to detail the build process is to check out the photos at this website: www.scalviniracing.com/ eng/factory.jsp. When it came time to slip the pipe onto our bike, we were a little nervous about everything lining up properly because of the hands-on manufacturing. Foolish us; the fit was perfect.
Just rolling on the throttle at low rpm, the motor seemed to pull a little harder and wanted to rev quicker. This feeling continued into a meaty mid that continued to a higher rev ceiling. The Scalvini is the only pipe that felt like it increased power throughout the entire powerband and provided an increase in over-rev. The bike seemed to build revs quicker than some of the other pipes tested. The PC pipe is the only one that felt stronger on the very top, though the Scalvini provided more bottom and mid gains. For the rider who can justify the price, the Scalvini is a great exhaust pipe.
BILL’S PIPES MX2 WORKS
Those too young to remember the glory days of the two-stroke motocross world probably aren’t familiar with the name Bill’s Pipes. Back in the day, Bill’s was a major player in the expansion-chamber wars. At one time he built pipes for the “Big Four” factory teams—Honda, Suzuki, Kawasaki and Yamaha—as well as several big-name dirt-trackers. The MX2 pipe is constructed from 19-gauge carbon steel and has an un-plated finish. Each section is beautifully hand-welded, and the mounting brackets fit right.
While we were mounting this pipe, several “old guys” walked over and said they remembered using Bill’s Pipes on their bikes and wanted to know if this one worked the same as the old ones. The short answer is yes. The bottom is quite a bit softer than the stock KTM exhaust, requiring a stab at the clutch to get the motor “back on the pipe.” The transition from bottom-to-low mid is still a little soft, but upper midrange to top end is a whole new ball game. Once the rpm starts to climb, the Bill’s pipe hits fast and hard. The top-end over-rev is huge with this pipe, allowing you to pull a gear longer than any other pipe we tested. On one section of our test track, with the stock pipe, third gear would sign off, requiring a shift to fourth gear to downside a long double jump. With the Bill’s pipe, the motor was still pulling in third at the jump face, and we actually had to be careful not to over-jump. This pipe felt like it produced the most upper-rpm power in this test. Approaching red line, the power would slowly taper off, feeling like it was being held back. Of all the pipes tested, this one required the most attention by the rider. If the motor was allowed to drop too low in the rpm range, a downshift was often required to get things going. On slick or slimy soil, too much throttle would light the back end up. For the rider who stays focused, however, the Bill’s pipe will make his bike a rocket ship.
The KTM 300XC doesn’t come equipped with a U.S. Forest Service-approved spark arrestor. If you plan on using your bike in the off-road arena, an approved muffler is a must. Modern spark arrestors work so well that there’s no reason to ride without one and risk getting that big-buck ticket. We tested a mixture of both spark arrestors and straight moto mufflers, naturally leaning toward the forest-legal models since the stock KTM muffler is a very competent unit.
Donny Emler is a hard-core two-stroke lover, so he took the reins on the development of this exhaust. Compared to the stock muffler on the 300XC, the FMF unit is noticeably quieter, and the weight is the same at 4 pounds 1 ounce. FMF uses their internal baffle system to meet the mandated 96-decibel sound level set by the U.S. Forest Service. The Q-Stealth has a larger canister, which provides room for more packing material, allowing you to go longer between rebuilds. The canister is constructed from aluminum with a stainless steel end cap.
We noticed with the first twist of the throttle that the sharp cracking sound of a two-stroke exhaust is a little more subdued. For us, that in itself was a huge plus, since we’re big proponents of the “less sound equals more ground” motto. On the track, the Q-Stealth softened the power everywhere—not to the point of stifling the ride, just less snap and bark. In slippery or loose technical sections, the smoother bottom-to-mid power transition can make things easier, providing more forward momentum and less spinning. The top doesn’t feel as though it pulls as hard or long as the stock fully open muffler. This is much more noticeable on the motocross track than it is in the off-road world. Since this is an off-road-legal spark arrestor, it’s not really fair to do a straight-up horsepower comparison to a closed-course-only system. Compared to some of the older USFS-approved exhausts, the FMF Q-Stealth is a major improvement. The Q-Stealth will slip on to your stock exhaust pipe. Mounting grommets and spacers are provided, and we can tell you that serious hard-core enduro riders prefer the hitless roll-on, the enhanced traction and the softer roar.
PRO CIRCUIT TYPE 296 S.A. SILENCER
Pro Circuit offers their Type 296 S.A. silencer for those looking to meet U.S. Forest Service sound and spark regulations. The 296 uses an internal metal baffle, chambers and sound-absorbing materials to meet the 96-decibel max sound level. It’s constructed using an aluminum canister with a stainless steel end cap. The canister is longer than a regular muffler’s to provide more sound-absorbing material.
The PC 296 does what it’s supposed to do with the noise issue; it noticeably reduced the volume on our KTM. On the track, the muffler exhibited the same power-changing characteristics that are common with spark arrestors. The entire rev range was softened. There was a little less hit down low and not quite as much over-rev pull on top. As a spark-legal muffler, the Type 296 is a top performer, as the softer bottom makes it easier in traction-challenged areas while still pulling quite well on top. The Type 296 fits right on your stock exhaust pipe and comes with all required mounting hardware.
SCALVINI ALLOY SILENCER WITH CARBON FIBER END CAP
The Scalvini silencer is not a U.S. Forest Service-approved spark arrestor; it’s a closed-course race muffler designed to complement their pipe. The muffler has an aluminum canister with a carbon fiber end cap. It has an open-core system like the stock KTM muffler. It comes with a metal strap that has to be wrapped around the canister to form a mounting bracket. The strap itself was easy to form around the exhaust and held securely. The issue we had with ours was that the bolt and spacer wouldn’t work on our frame. The bolt had the wrong thread pitch, and there seemed to be a spacer missing to fit inside the rubber grommet. We remedied this by borrowing the spacers from our FMF muffler, which fit right on. Like the pipe, the Scalvini muffler is a work of art. The decibel level was the same or slightly quieter than that of the OEM muffler. This was a little surprising, since the canister is only 12 inches long, 5 1/2 inches shorter than the KTM muffler.
Typical of a shorter muffler on a two-stroke, this one makes the motor snap to life sooner. With the pipe, this system really makes the KTM rip. The power comes on faster and harder than with the stock muffler. As a full-race package, the Scalvini pipe and muffler combo resulted in the greatest power gains we experienced. The only drawback to the combo is that the short muffler made the power almost too intense, too instant. This could prove to be a handful in low-traction conditions. On our tacky test track, this combo was lethal—but so is the price tag. It’s not a cheapie.
The MX2 Silencer is designed to work with the Bill’s MX2 pipe, meaning it’s a pure moto muffler. The silencer is constructed from lightweight 6061 T-6 aluminum for the canister and uses 304 stainless steel for the mid-pipe. The canister measures 10 1/2 inches long as opposed to 17 1/2 inches for the stock KTM muffler. This makes it a “shorty muffler,” which means it’s quite a bit louder than the OEM muffler. For a closed-course-only muffler, the MX2 works beautifully with the MX2 pipe. It allows the power to come on a little sooner and starts pulling harder in the mid before signing off in the upper stratosphere. The MX2 silencer really wakes up the power characteristics of the Bill’s pipe. The only real issue is the sound level. It’s too loud for anywhere other than the racetrack, but that’s what it’s designed for. o